Nader explained that he had planned to organize a slate of six candidates to primary Obama on a variety of issues. The plan didn’t work out though, Nader said, partially blaming those who are working to get Obama reelected.

“The minute any name was mentioned ... they made the calls,” Nader said of the White House’s efforts. “They jumped like a cat.”

For example, he said if former Sen. Russ Feingold (D-Wis.) had opted to run against Obama, his future in the Democratic Party would be finished.

Feingold, who considered running for the White House in 2008, has repeatedly said he will not challenge Obama and supports the president’s reelection efforts.

Obama’s reelection campaign strongly denied it discouraged potential primary candidates. In response to the campaign’s comments, Nader said that it wasn’t necessarily an official effort, but certainly came from people with close ties to the White House and Obama’s bid for second term.

There were other reasons why Nader’s initiative collapsed, he said. He cited the New Hampshire secretary of State’s decision to move the state’s primary up to Jan. 10. Nader and other liberal activists had wanted to make a big splash in the Granite State, which holds the first-in-the-nation primary.

But the state’s scheduling decision minimized the amount of time to get organized.

Still, Nader said he was able to line up candidates for a primary challenge, including a former congressman. He would not name names, citing the fear of political retribution.

Nader and others on the left have been disappointed with Obama’s presidency, citing the Afghanistan war, the lack of a public option in healthcare reform and the 2010 extension of George W. Bush’s tax rates for the wealthy.

Nader said the goal of a primary challenge would not have been to defeat Obama. Instead, it would have forced Obama to pay more attention to his liberal base, he maintains.

Last summer, Rep. Peter DeFazio (D-Ore.) said a primary contest would benefit the left because it would “give us back the candidate we had three years ago.”

Rep. Dennis Kucinich (D-Ohio) at that time said a primary challenge would be “healthy” for the Democratic Party.

Others have also pointed to Nader’s 2000 bid as a spoiler for Gore. In the swing state of Florida that year, Nader received 97,488 votes. Gore officially lost the Sunshine State by 537 votes.

While parts of the left are dismayed with Obama, there are many leading progressives who believe a primary challenge would be political suicide.

The co-chairmen of the House Progressive Caucus, Reps. Raúl Grijalva (D-Ariz.) and Keith Ellison (D-Minn.), have both said the Democratic Party needs to be 100 percent behind Obama.

Ellison in September claimed a primary opponent would “undermine our unity, and we need everybody in the same boat.”

Former Rep. David Obey (D-Wis.) this week said that Nader “bears a lot of the responsibility for George W. Bush for eight years” and scoffed at the effort to challenge Obama from the left.

Obey told The Hill, “I mean let’s get serious: We have the gravest threat to progressive government that I have seen in all the years I've seen in politics.

“And if Obama can’t win in the next election, progressivism will take a huge, huge hit. Anybody who wants to nitpick with him as the nominee of our party is smoking something that isn’t legal. It’s ridiculous. I mean we will rise or fall based on how Obama does.”